There are living fossils swimming in Minnesota rivers, and the DNR is working hard to make sure they stay there. American paddlefish have existed since dinosaurs roamed the planet and can reach lengths of seven feet. These gentle giants only eat plankton, which they find with their electro-sensitive paddles – or rostra (singular: rostrum).
Paddlefish were once abundant in the Mississippi River drainage, including the Minnesota River. By the late 1800s, though, their populations were in decline because of overharvest, pollution, and the damming of their native waterways. Their valuable roe has been sought for caviar as well. Eventually the Minnesota paddlefish population was so decimated that it became listed as a threatened species, and both recreational and commercial fishing were prohibited. In fact, before 2016, only one paddlefish had ever been caught by the DNR in the Minnesota River.
Fortunately, paddlefish populations nationwide have been making a comeback, thanks to federal stocking efforts and state conservation action. In Minnesota, habitat restoration, dam removal, water quality regulations, and strict angling regulations (anglers may not target paddlefish) have made recovery easier for local populations. As the species rebounds, more focus is being put on studying growth, abundance, and movement. The DNR’s paddlefish research in the Minnesota River is financed by the Minnesota Environment and Natural Resources Trust Fund, and the results are encouraging.
Eighty-two paddlefish have been caught by the DNR since 2016, and 14 of these have been outfitted with acoustic transmitters that allow DNR scientists to track their movements. The findings were somewhat surprising. Paddlefish in the Minnesota River are highly mobile, traversing from Granite Falls to the Mississippi regularly. Each year, they reconvene in groups of upwards of 50 in specific spots. It isn’t clear why they pick these particular spots, but they regularly return to the same ones year after year.
DNR crews survey paddlefish in the Minnesota River each fall, when heat stress to the fish can be avoided. The survey begins with the team scanning for the acoustic tagged individuals in the areas where they were first captured or last detected. On this particular survey, six unique acoustic pings were heard, a sign of six paddlefish close by.
After scanning, the crew then drifted floating 5” gauge gillnets along likely pockets. Because the mesh is so wide, there is hardly any bycatch of non-target species. In deep areas, the 10’ nets may fail to sample thoroughly, so the crews might set longer, stationary nets in an arc around shore. Any paddlefish that run into the nets become tangled but remain unharmed.
After pulling the fish gently from the gillnet, the crew lowers each one into a trough of oxygenated water. Then the fish are checked for acoustic transmitters, PIT tags, or jaw bands, which would mean that the individual had been caught previously. Each paddlefish is measured and weighed, and all new fish are PIT tagged and jaw banded. Then they are released close to where they had been captured.
At the end of this survey, 12 paddlefish had been sampled from one small stretch of river. What was most surprising was that none of the 12 had an acoustic tag, even though six had been marked. This implied that there were many more paddlefish in the area that had not been caught, a cheering thought for conservationists.
Tony Sindt, Minnesota River Specialist, says that the future for paddlefish is bright. Large populations have been seen not only in the Minnesota River drainage, but in other drainages as well. “When I first started in this position, the thought was that you might see six paddlefish your whole career,” remarked Sindt, who has now handled dozens.
Sindt continued on to share that given the number of paddlefish living in Minnesota Rivers, reproduction may very well be occurring in our state, something previously unconsidered. The numbers don’t lie, though, and this species seems well on its way to recovery.